public class MyLinkedList {

    public ListNode head;
    public ListNode last;

    class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }

    public void disPlay() {
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }

    public int size() {
        int len = 0;
        ListNode cur = head;
        while (cur != null) {
            len++;
            cur = cur.next;
        }
        return len;
    }

    public boolean contains(int key) {
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        if (head == null) {
            head = node;
            last = node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    public void  addLast(int data) {
        ListNode node = new ListNode(data);
        if (head == null) {
            head = node;
        }else {
            last.next = node;
            node.prev = last;
        }
        last = node;
    }

    public void addIndex(int index,int data) {
        ListNode node = new ListNode(data);
        if (index < 0 || index > size()) {
            throw new LinkListException();
        }
        if (index == 0) {
            addFirst(data);
            return;
        }
        if (index == size()) {
            addLast(data);
            return;
        }
        ListNode cur = findIndex(index);
        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;

    }

    public ListNode findIndex(int index) {
        ListNode cur = head;
        while (index != 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }

    public void remove(int key) {
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    }
                } else {
                    cur.prev.next = cur.next;
                    if (cur.next != null) {
                        cur.next.prev = cur.prev;
                    }else {
                        last = cur.prev;
                    }
                }
                return;
            }
            cur = cur.next;
        }
    }

    public void removeAllKey(int key) {
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    }
                } else {
                    cur.prev.next = cur.next;
                    if (cur.next != null) {
                        cur.next.prev = cur.prev;
                    }else {
                        last = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }

    public void clear() {
        ListNode cur = head;
        while (cur != null) {
            ListNode nextNode = cur.next;
            cur.prev = null;
            cur.next = null;
            cur = nextNode;
        }
        head = null;
        last = null;
    }


}
